Switching apparatus



F. ALDENDORFF.

SWITCHING APPARATUS.

APPLICATION FILED MAR. 16, 19M. RENEWED FEB. 3,1920.

1,348,835, Patented Aug. 3, 1920..

9 SHEETS-SHEEI 1.

Fig.1!)

Wfi'nessesi Invenmr:

F. ALDENDORFF.

SWITCHING APPARATUS.

APPLICATION FILED MAR.16,I914. RENEWED FEB.31920.

Patented Aug. 3, 1920.

9 SHEETS-SHEET 3.

Wilnesses: Jnverflur:

F. ALDENDORFF.

SWITCHING APPARATUS.

v 7 APPLICATION FILED MAR.|6,1914- RENEWED FEB. 3, 1920. 1,348,835.Patented Aug. 3, 19200 9 SHEEIS SHEET 4.

Wiin E55Es: lnveninr:

F. ALDENDORFF;

SWITCHING APPARATUS.

APPUCATION FILED MAR. 16, 1914. RENEWED FEB. 3,1920.

1 348,835 Patented Aug. 3, 1920.

9 SHEETS-SHEET 5.

Fig.5.

F. ALDENDORFF.

SWITCH-ING APPARATUS.

APPLICATION FILED MAR. 16, 1914. RENEWED FEB. 3. 1920.

1,348,835. at tedAilg- 3,1920.

9 SHEETSSHEET 6.

Wflnesses: f 111v 211101: 2??? I 355 j; imam g F. ALDENDORFF.

SWITCHING APPARATUS. E

APPLICATION FILED MAR. 16. 1914. RENEWED FEB. 3.1920.

- 1,348,835, Patented Aug. 3, 1920.

9 SH EETSSHEET 7.

Fig. 3.

Wirnesses: Jnvenhnr:

jg 1 I 64. @6 7 F. ALDENDORFF.

SWITCHING APPARATUS.

APPLICATION FILED MAR. 16. 1914. RENEWED FEB. 3. 1920.

Patented Aug. 3, 1920.

all, his. lsi

Fig. 9.

Wiinesses:

F. ALDENDORFF.

SWITCHING APPARATUS. APPLICATION FILED MAR. 16. 1914. RENEWED FEB. 3,1920.

Patented Aug. 3, 1920.

:UNITED STATES PATENT OFFICE.-

FRITZ ALDENDORFF, OF VJILMERSDORF, BERLIN, GERMANY.

SWITCHING APPARATUS.

: Specification of Letters Patent.

Patented Aug. 3, 1920.

Application filed March 16, 1914, Serial No. 825,102. Renewed 'Fetruary3, 1920. Serial No. 356,000}.

To all whom it may concern: 7

Be it known that I, Fnrrz ALDENDoRrr, a subject of the liing of GreatBritain, residing at 32 Mannheimerstrasse, l lilmersdorf, Berlin,Germany, have invented certain new and useful Improvements in SwitchingApparatus, of which the following is a specification.

illy invention relates to improvements in stones for interconnectingtelephone lines electro-mechanically controlled switches. ihe object ofthe invention is to provide an improved percentage system in which :.i"ik-acting line finders connect calling sub- )ers to idle selectors soquickly as to inall selecting impulses which calling 5; received by theselectors, instead of railing to reach them on account of thecallsubscrihers commencing to work their else transmitters before theline finders we Eiumd time to connect them to an idle selector.

nick-acting finders are expensive an; number should be reduced to theutt limit. In order to attain this object cup of comparativelyslow-acting finders and another group of quick-acting finders isprovided for each group of subscribers. ii hen a subscriber makes a callhe is rapidly connected to idle selector by a quiclcactn finder so thatthe subscriber can immo- .tely commence sending impulses. Thisconnection through the quick-acting finder is maintained until theconnection with the desired line is established or until the conncctionhas progressed to a certain stage when it is substituted by a connectionthrough a comparatively slow-acting finder that maintains theconnection'until the end or .he conversation. The quick-acting finderwhich was only used for a few seconds is immediately made available fornew connections. With this arrangement two or three quick-acting finderswill be sutficienttor a group ct two or three hundred subscribers. Thenumber of slow-acting finders willbe equal to the greatest number ofsimultaneous conversations in the busiest hour. Associated with eachquick-acting line finder is a selector finder which always keeps itsquickacting finder connected to an idle selector. The selector finderskeep traveling over contacts connected to selectors until a contact orother selector.

ice-rs intend to deliver to the selectors ncctecl at the ing to an idleselector is reached. It stops at us trunk rendering it engaged andkeeping it ready t'or the next connection that is to be ade through itsquick-acting finder. hen tins connection has progressed through theexchange switches to a certain stage (6. 9. up the point where the firstor second selector has been started hunting for an idle trunk leading toa certain group) the selector finder receives a starting current thatstarts it hunting for another trunk leading to an- There are fewerselector finders than selectors and there will never be more than oneselector finder connected to any trunk.

The first group selectors associated with the slow-acting finders are soarranged that when a talking connection is extended through one of themand through a second selector or final selector certain functions willoccur simultaneously in the first group selector and the second groupselector or in the first group selector and the final selector. Forexample, in the moment when the action of the final selector changesfrom selecting a certain row of contacts to selecta certain set ofcontacts in a row a startng circuit is closed in the group selectorwhich causes the selector finder that is contime to the group selectorto start moving so as to sever its connection with the group selectorand to hunt for an idle group selector to which it may connect thequick-acting finder that is associated withit. The moment the connectionbetween a group selector and a quick-acting finder is severed in themanner just described a new connection is made between the calling lineand the group selector through a comparatively slow-acting finder, theslow-acting finder having prepared this other connection during the timethe calling subscriber or the semi-automatic operator was sending theselecting impulses to the group and final selectors.

the system described herein a set of selector control relays is used ofwhich the release and change over relays have their battery circuitnormally open, the closure of this battery circuit taking place at themoment the slow-acting finder associated with the group selector towhich the set of relays belongs is moved out of its normal position.

My invention will be fully understood from the following description andby reting finders,

of a selector erence' to the accompanying drawing in which- Figure 1 isa general diagrammatic rep- 'resentation of the new system, 7 v V Fig. 2indicates diagrammatlcally the arrangement of the bank contacts andmovable brushes of a quick-acting finder and the order in which thelines of a group are connected'tothe bank contacts of the quickactingfinders belonging to that group,

Fig. 3 show's partly in perspective View and partly diagrammatically theconstruction of a quick-acting line finder,

Fig. 4 illustrates the circuits of the subscribers line'and'cut-ofi"relays, the connections between the subscribers line relays and thegroups of permutations or guide wires used for guiding the quick-actingline finders to a calling line, and the circuits of a finder starter,

Fig. 4 represents connections that join 'atthe top to correspondingwires of Fig. 8,

at "the bottom to the wires of Figs and at the right to wires (Z55, 055.7255, 6055, etc., issuing from Fig. 5.

' Figs. 5 and 6 show the circuits of the quick-acting line finders.

Fig. 7 indicates the circuits of the selector finders,

Fig. 8 shows the circuits of the slow-act- Fig. 9 the circuits of agroup selector,

g. lo'the circuits of a final selector or connector.

Fig. 11 is a simplified showing of the circuits by which the slow-actingfinders are caused to connect to a calling line and Figs. 12 and 12*"show circuits forpreventing" more than one slow-acting finder fromconnecting to a calling line atthe same time. i

,A complete'diagram of the whole system is obtained by placing Figs. 4,5 and 6 beside each other and Fig 1 above Fig. 4:, Fig. over Figkii,then Fig. 8 over Fig. 3, Fig. 9 over Fig. 7 and finally Fig. beside Fig.9. 1

The manner in which connections are established with the new system canbe explained in a general way by the aid-of Fig. 1. The subscribers T Tetc., are all con-, nected to the bank contacts of three different kindsof switches, viz. the quick-acting finders F, the slow-acting finders LFand the final selectors LlV. If there are more than one group ofsubscribers in the exchange group selectors GW will be providedfin themanner indicated.

.lVhen a subscrlber 'calls by removing his receiver from its switchhooka quiclcacting finder F immediately (or after. it has executed a shortmovement) establishes a conncction between the calling subscriber (e; g.T.) and a group selector 'GVV by the aid finder VS which always keepsgroup selector GW selector tors, or even the finder F associated with itconnected to an idle group selector GlV or slow-acting finder LF.

The calling subscriber now causes the to select the desired 'roupandobtains a connection with an idle final selector LW in that group.Themoment the subscriber calls the slow-acting finder LF associated withthe group selector GlV is started and while the group selec- "tor isexecuting its selecting function the out its slow-acting finder will becarrying -When operation of finding the calling line.

the slow-acting finder and the group selector have executedtheirfunctions the connection through the quick-acting finder F and thefinder VS is dissolved so that only the connection through theslow-acting finder LF i'emains. The subscriber (or semi-automaticoperator) now sends the remaining selecting impulses, which may berequired for putting the final selector 11W 011m the desired line (6. 9.T through the'slow-acting finder LF and through the group selector GVVtothe final selector.

If the groups of subscribers are large 6. g. if they contain as many asfour hundred subscribers it will happen that a slow-acting finder willtake a comparatively long time to. find the calling line T In ordertogain this time the circuits for casting oil or disconnecting thequick-acting finders from the first group selectors may be arranged sothat they act only after the second selecthe final selectors'havecarried out their selecting functions.

.Inthe l representation of the invention shown in this specification thecasting otf circuit acts when a final selector has half done its work2'. c. after it has selected the row of contacts containing the wantedsubscribers line. 1 InFig. 2 are illustrated the ten rows of contacts ofa hundred point quick-acting line finder. The hundred lines of a hundredgroup are connected in the order indicated by the numbers. For examplethe lines numbered from O0 to 09 are connected to the bank contacts ofthe first row. The lines numbered 10 to 19 are connected to the secondrow of bank contacts and so forth. All the lines with units digitsranging from 0 to 4. are connected to the left half of the contact bankand all the lines with units digits from 5 to 9 are connected to theright half of the bank. p v 7 For each row of contacts there is a wiper7.0 to 20 The line-finder is so arranged that according as thesubscriber calling is connected to the left or right half of the contactbank the wipers 20 to 10., will move from their middle position to theleft or right. The farthestdistance that the wipers wiper W moves towardthat when ci is magnetized the The Wipers w to 10 are normally insulatedso that no connection is made to the calling line by these wipers alone.Th'ere is, however, another wiper W that is connected to a trunk or linkcircuit which cooperates with the wipers 'w to 10 This the upper orlower half of the contact bank accordingas the calling line appearsinthe upper or lower half. The wiper /V stops moving when it reaches thewiper 10 in the row containing the bank contacts or the calling lines.The greatest number 01 rows traversed by the wiper WV is five. Both theset of wipers 20 to w, and the wiper EV travel simultaneously. Thereforethe maximum time required for the finding of any one line out oi ahundred'is the time that a wiper w or W takes to move'five steps'and theaverage'time required is the time needed for 2.5 steps.

ii means which may be used for propelling the wipers 20 to w of thequick-acting line finders is shown in Fig. 3 in which S is a wiper shaftbearing the wipers 10., to w and journaled in a bearing 6. At thebottomend of the wiper shaft is fixed a disk 03. This disk (Z is driven byanother disk 6Z or (Z fixed to a driving shaft S that may be common to alarge number offinders or selector switches. 0 and 0 are solenoids whichon being energized by an electric current magnetize their respectivedisks (X or (5 and then attract the other rim or the flexible disks d totheir respective disks (Z or The shaft S with the disks (Z and d rotatesin the direction indicated by the arrow "((4) so wipers 20 to 10, willrotate toward the left of the contact bank and when 6Z2 is magnetizedthese wipers will be rotated toward the right half off the contactchankfThe wipers 20 to 20 each consist of a pair of brushes of which the upperone engages with the contacts belonging to the various subscriberscontained in its particular row and the lower one slides upon acontinuous contact piece, a. y., 39 Each contact piece p to p, isconnected to the fixed contact of a secondary switch SW The secondaryswitch is constructed like the orimar switch PS 'ust described, exceptthat it has only one row of bank contacts and one'wiper W instead often. The wiper V is moved by its solenoids or magnets 0 or 6 toward itslower or upper five contacts connected to the lower or upper fivecontact pieces PO to p or 29 to 92 respectively. 7 7

Fixed to the upper end ofthe shaft S is a disk riphery. Projecting intothis slot is a tongue r attached to a switch 6Z8. When the shaft E5 isrotated in the direction of the arrow (1 the tongue 6' slides up ontothe top of the disk (Z, and causes the switch (is to to 20,, that issituated (Z; having an oblique slot Z at its peclose its top contact 0but when the shalt S is turned in the direction oi the arrow (1 thetongue 5 slides down and rides on the bottom of the disk (Z and closesthe contact 0 of the switch dc. This switch is used when restoring thefinder to its normal positionas will be fully described later. Thesecondary switch o d is also provided with a switch similar to (55-, butthis is not shown in Fig. 3.

The shaft S of the quick-acting finder also has a cam (Z which moves anoffinormal switch the functions or". which will be fully described latei ilthough for simplicity of illustration only one wiper in and one setof bank contacts per row is shown in Figs. 2 and 3. three wipers andthree row are used, an SlV four wipers contacts are provided as shown inthe cuit diagram in 4.

in Fig. 4 S S S etc., represent the subscribers stations of group of onehundred subscribers. The stations S S and 7 sets of contacts per on thesecondary switch W and four sets of bank Pr 3 represent the first andfifth, and

finder contac u two S .re siown connected to their 31) bank contacts.

The first quick-acting finder F of the hundred group is represented byfour oi its ten sets of wipers wall, @050, e000, eccl0-wa1, 1051,1001,w. Z1wa5, v0.35, 1on5, code-1M6, 7.0126, c006, 2066 belonging to theprimary switch and the set of wipers 10 belonging to the secondaryswitch of the finder. The primary and secondary switches each have anadditional wiper VV and VV E and E are the motor magnets of the primaryswitch and E and E represent the motor magnets of the secondary switchof finder F DS 6, is the switch corresponding to (Z8, Fig. 3, belongingto the primary switch D5 a similar .witch belonging to the secondaryswitch ofthe quick-acting finder F OS is an ofi normal switch on finderF tp and are test relays and r is a release relay ot' finder F Therelease relay controls four switches, r r r 0% which, in order tosimplify the drawing, are shown near the motor magnets E that theycontrol. The switches are shown in their normal position. lVhen therelease relay r is energized it moves these' switches from "their backcontactsto their 'i'ront contacts.

The finder F, is also provided with a coir necting relay CR whichextends the line of a calling subscriber to the next switch orselector,V Fig. 7, the moment the finder hasfound the calling line.

There are as many quick-acting finders in a hundred group as requiredfor the monient of maximum traffic, say two crthree. F representsanother quick-acting finder 1n the same hundred group. Only as many ofthe parts of this finder are shown asare sutficient to make the s istemcomprehenfunctions of which wiil be explained presently. The bankcontacts 10 to 39 and 7), to

7 p of allithe finders of a hundred group are connected in multipleftothe groups of per; mutation wires, (it-+9 and 01 -9 Each hun- V dredgroup hasits'own twogroups of permutatioirwires. p '7 Each of thehundred snbscribersi f ahnndred group is-connected by a set ofmultiplewiresrsuch as 04 or ()5 to a set of banlr contacts in each'quick actingfinder F oi the group, these sets ol banl contacts being 7 traversed bysets of brushes m, 106,"?00, rod.

The subscribers lines are connected to the bank contacts in the orderillustrated in the first row, wipers @0661, 1051,1001,

Fig. 2. Subscriber S is connected to the first set of bank contacts inthe first row, S v is connected to nectionsof two subscribers, OA-and'05 in in the sixth row of bank contacts are fully shown. i r 7 Thewipers @0610, 1050,- 2000, wtZO traverse curl-l the second row, wipersc0415, @0725, e005, @0615 the sixth, wipers each, e056, e006, wd6, thesev enth row of bank contacts. Thelwipers and bank contacts otv thethird, fonrth,, fifth, 7 eighth, ninth and'ten'th rows areomitted in ,7

' are arranged. to control by the first lower order to simpliiycthedrawing. I

The wipers m0, 1050,0000, 40610 of the first row are connected by a setof wires @0 to the first set of bank contacts on the secondary switch ofthe finder, the wipers cool, 1051,4001, wrll, of the second row to thesecond set and so forth. p c

In orderto connect a certain subscribers line, as 04; to a trunkline-a,6,0, (Z leading to a selector, Fig. 7, all the sets of wipers line 04:and the set or secondary wipers the second set ofcontacts I in the row,S to the third set in first 7 f row and so forth. In Fig. 5 only thecon} 7 the firstrow and two subscribers, 5'4: and 55,-

teases-s 'LliaQ whOpwhl),' u iZO; mi, 11151, @001, wdl,

etc., are an" ed soas to bring onset the sets of wipers 'e. 9. me,@0120, e000, @0520 onto the contacts that is connected to the N isturnedso as to connect to the set of priset of bank mar wi )ers e. r.cod-(i i069 acct); wa l) that is touching the subscribers line. Thesubscribers' line, 04, will :then be connected through we, 1000, i000,molt), vi -V7 to the trunk to, b, 0, d. p 7

if a calling subscribers line is connected to a set of bank contactslocatedin the half 01"" the contact bank shown above the sets ofwipers-20660, 1050, 1060, ado, Qua-l, 'Ll'ibl, cool,

Q5451, etc, a motor magnet E similar to 6 Fig; will come into-action andwill more v all the wipers toward the ujper half of the bank, If thesubscribers line is connecter to the lower -half of the bank the motormagnet 15,, similar to 6 Fig. 2, will be energized and will more all thewipers of the primaryswitch -toward the lower half.

5 It the calling subscriber is connected to the half of the contact bankshown at the left of the line thewipers V7 ot the sec-' ondary switchwillbe moved by the motor magnet L tothe setsoicontacts'connected to thewlpers 10640, 1060, me, and, @0541, 10b1,

, 1004i, wad, located at the 1001, m1, wael, 107A; left ctthe line m yandif the calling subscriberis connected to a set of bank contactssituated at'the right of "the line: 00- 1 the wipers W will be moved bythe motor magnet E toward the, secondary bank contacts that areconnected to the sets of wipers 10665, @065, e005, wa5 to c0009, e069,e009, 'wd9located at the right side of the line 00 9 The directionofmoyement of the wipers is thus dependent on" the partof the contactbank of the quick acting finder that a calling subscriber'is connectedto. The subscribers c unconsciously determine these directions ofmovement by IIlGZlIlS'Oi. relays m m and m 722 and by circuits connectedto their line relaysl Z etc.

The relays m m determine the direction of movement of the primary switchwipers waO, @0120, e000, @0030, etc, and the relaysm V m determine thedirection ofmovement ot thesecondary switch wipers 10 All thesubscriberswith units digits ranging from 0 to 4L are connected to thebank contacts shown in :Fig. 5 in the lower half of thebank. Thereforeall these subscribers armature contacts 100 ottheir line relays thecircuit do of the relay m which closes the circuit of the motor magnet Eand thus the subscribers with these units digits are connected to theupper half of the bank.

All the subscribers of the group with tens digits ranging from 0 to 1are connected to lank contacts shown in Fig. 5, at the left side of theline ag the wipers W oi the secondary switch are moved toward the theupward motion magnet, E for all wipers 20 'w "w 20 etc, by the motormagnet E which is controlled by the relay wi Therefore all thesubscribers with tens digits ranging from 0 to 1- are connencted by thecontacts 101 of their line relays to the circuit 1 connected to theleftward motion relay m All the subscribers with tens digits rangingfrom 5 to 9 are connected to bank contacts shown at the right side ofline 512-3 in Fig. The motor magnet E that causes the wipers to traveltoward the primary wipers in the right half of the bank is controlled bythe rightward motion relay 772 and therefore all the subscribers withtens digits ranging from 5 to 9 are connected by their armature contacts101 to the circuit of the right ward motion relay m It is thus seen thatthe relays m m indicate whether the calling subscriber is connected tothe upper or lower half of the contact bank and that the relays wi mindicate whether the subscriber is in the right or left half of thebank.

The relays m m ,'m errtaken together indicate what quarter or thecontact bank the subscriber is in. If the subscriber is in the lowerleft hand quarter for example the relays m and m would be energized soas to energize the motor magnets E and E The particular line in thequarter of the contact bank indicated by the relays 1a,, m 772 m isindicated by means of the permutation wires 0 to 9 and 0 to 9 Thepermutation wires 0 to 9 determine the point 7),, to g), at which theprimary guiding wiper W shall stop and the permutation wires 0 to 9determine the point of stoppage of the secondary guiding wiper W Thepermutation wires 0 to 9 and 0 to 9 correspond to the units and tensdigits respectively of the calling subscribers. The contact 102 of theline relay 1 of subscriber 00 is connected to the units permutation wire0 and contact 103 of this relay is connected to the tens permutationwire 0 The contacts 102 and 103 of subscriber 01 are con nected to tenspermutation wire 0 and to units permutation wire 1 respectively. Thusthe connections between the permutation wires and the line relaycontacts 102 and 103 of the hundred subscribers differ so as to producehundred diflerent permutations, and each permutation represents adifferent combinative setting of the primar and sec ondary switches of afinder F l Thus if subscriber 05 calls the primary switch of the finderwill be moved so as to bring the guiding wiper /V into connection withthe units permutation wire 5 and the secondary guiding wiper W will bemoved into connection with the tens permutation wire 0 and as the setsof brushes waO, 1060, i000, wal0-wa1, Q0711, wcl, wdl, etc, and aremoved in unison with their guiding wipers the subscriber 05 would beconnected through the sixth set of bank contacts that IS COIIDQCtGCl inthe first contact row to the wires 05 and through 1000, 2060, 2000,wcZO- W V to the trunk a, b, 0, (Z.

It will now be assumed that a subscriber e. g. No. 59 makes a connectionwith another subscriber.

lVhen the calling subscriber S 59 removes his receiver from theswitchhook he closes his line loop (4 6 in a well known manner and hisline relay Z is then energized by a current flowing from the negativepole of the exchange battery through the contact 110 of the finderstarted FS, common feed wire 111, contact 105 of line relay Z 112, 6 64113 to earth. Line relay Z is energized and opens its contact 105 whileclosing its contacts 100, 101, 102, 103 and 104.

Since the subscriber S is connected to a set of bank contacts located inthe upper half of the contact bank and to the right of the line wtheupward motion relay m and the rightward motion relay m must be energizedin order to set the finder-onto the calling line. Therefore the armaturecontacts 100 and 101 of the line relay Z are connected to the circuitsat and M and the relays m and m are energized by circuits from thenegative pole of the battery through F55, m a, 100 to earth and from thenegative pole through m M, 101 to earth. At the same time the tenspermutation wire 5 and the units permutation wire 9 are earthed bycontacts 103 and 102 respectively.

The upward motion relay m closes its armature contact 114 and prepares acircuit for the upward motion magnet E and the rightward motion relay mprepares a circuit at its contact 113 for the rightward motion magnet EThe finder starter F S is energized in series with the relay m and byattracting its armature 116 momentarily closes the contact 117. Thiscauses a current impulse to flow from the negative pole through 117,starting wire ST, contacts 119, 118 of the oil-normal switch of thefirst idle finder (e. g. F 1), wires 12 1 and 118 magnets E and Econtacts 128 and 132, wires 7 2' u, contacts 115 and 11 1. The magnet Eis energized and moves the wipers W WV, of the secondary switch one steptoward the right hand wiper wires @0 w and the magnet E is alsoenergized and moves the. wipers wail), wlzQ, 10,00 wdOwwcstarting wireis extended magnets E and E 40b e00 wd etc, and the guiding wiper WV ofthe primary switch one step upward.

It will be assumed for convenience of description that the magnets E E EE move their wipers by a step by step ratchet and pawl device so thatfor each impulse sent through these magnets their wipers are moved toanother set of bank contacts.

It will be noticed that two magnets E, and E are connected to the wire118'and two magnets E and E to the wire 12s. The impulse sent from thefinder starter FS over the starter wire ST will, however, always aitectone of the magnets E, or E and one of the magnets E or E only, becausethere will always be only one circuit of each pair of motor magnetsclosed by the relays m m m m Y On the primary switch of the finder beingmoved out of its normal position the offnormal switch ()3, closes itscontacts 120,

V 121 and-122 and opens its contacts 118 and 119. The primary switch isarranged to execute its initial movement when the startstarting wire Sceases,

mg impulse over the so that the contact 121 through which the to thenext finder F is not'closed before the starting impulse ceases and afalse starting of the next finder F does not occur. r r

' When the contact 122 is closed an interrupter 138 is connected to themotor magnets in place of the starting wire and current impulses thenflow from the negative pole through 183, 13a to the wire From the wire138 the impulses flow through the wires 139 and 1 10 to the'pairs ofmagnets E E E E Only the circuit of one magnet in each pair is closed bythe relay m m m m at any one time. In the case assumed the circuits ofmagnets E and E, are closed at 11% and 115 respectively. Therefore theimpulses flowing throrgh the wires 139 and 140 will energize only thecausing the wipers of the primary and secondary switches to be bothmoved upwardly.

It will of course happen that both switches will move downwardly, orthat the primary switch will move its wipers downwardly while thesecondary switch moves its wipers upwardly and vice versa.

In the case assumed the wipers will move upward one step andthe'circuit' 'ot' the magnet E will then. be broken by theene'rgiz'ation of the secondary test relay 8]), for a circuit'will beestablished for this re la'y by the secondary guiding wiper N. reachingthe tens permutation wire 5 This circuit may be traced from the negativepole through 141, 1 1-2 s22, p 5 1 13, 103 to earth. On the encrgizationof relay 8g) the circuit of magnet E is broken at 136 and the motion ofwhet-rs W il is stopped.

The wipers or. the primary switch will magnet E, at contact .made aconnection with the call continue their movement until the guiding wiperW reaches an earthed permutation wire, which in the case assumed will bewhen the permutation wire Q is reached. The circuit of the primary testrelay will then be closed from the negative pole through 141, tp, WV 9,14d, 102 to earth, and the test relay 23 will open the'circuit of the135, thus stopping the operation of this magnet. The wipers emf), a065,1005, wd5, will now be resting on the set of bank contacts Z1059 .towhich the subscriber 859 is connected, and the set 01 wipers W will beresting on the secondary switch contacts connected by N to 1/1145, 1065,c005, LU(Z5. Thus the calling line will be connected through its wires59, 6055), wao, 1065, c005, 10cZ5lV to the trunk a, b, 0, d.

The moment both test relays 51), t are energized, a circuit is closedfrom the negative pole through 137, 145, CR to earth and the connectingrelay CR then closes its contacts 146, 148, 1&9 while opening itscontact 134. By the closure of contacts 1&8, 1&9 the calling line isextended to the selector VS and the closure of the contact 1 16 resultsin the energization of the calling subscribers cutoff relay 00 by acurrent from earth through CR, 1 1-6, 1 17, 0, lower brush of N N0 bankcontact 0t line 59 on which lVc is resting, wire 0 connected to thisbankcontact, cut off relay 00 to the negative pole of the battery. Thecut ofi relay is energized and cuts the line relay Z oil of the callingline a 6 thus (lei-Energizing the line relay.

As long as a line relay is energized the upward motion relay m or thedownward motion relay on, will be energized in series with the finderstarter 'a nd the finder starter will keep open the common battery feed1 to all the line relays of the hundred at ill) any other subscrihor Butthis condietc...

1g ii a and as the average time required for this the time that it takesthe wipers to execute steps, the blocked condition of all the linesexcept the first one to send in a call onl lasts a fraction of a second,and a second subscriber sending in call would not notice and thusprevent the group from calling. t1on only lasts until a finder F has anydelay.

Each quick-acting tinder is always l connected toan idle slow-actingfinder or to an idle group selector Gll" by a se lcctor finder- VS, Fig.7, as will be present-iv more fully described. At the momentquick-acting -finder (c. 5 F is started a starting impulse sent throughthe st: wire St the slow-acting finder LF to w the quickacting finder isinccted by the selector findrr V9 is also c5 ivy on he pulse whichfiowsfrom the negative pole of the battery through contact 117 of the finderstarter, St, 118, wire 200, contact arm 201, 207, contact 213 of theoff-normal switch 05 of the slow-acting finder LF, motor magnet 214 01the slow-acting finder, 215, 216 to earth. Due to this current impulsethe set of brushes a bf, of, is moved by the rotary magnet 214 out ofits normal position whereupon the oil-normal switch OS closes it contact217 and causes an interrupter 218 to be connected to the motor magnet214. Current impulses will then flow from the negative battery polethrough 218, 217, 214, 215, 216 to earth and these impulses will causethe motor magnet 214 to alternately attract and detract its armature andto move the set of brushes cf, of, (Z) so as to cause it to trail overthe fixed sets of contacts of the slow-acting finder until the contactset is found to which the calling line Z is connected. As soon as thisline is reached a current will flow from the negative battery polethrough 219, contact arm 202 of the selector finder 208, relay 220,brush (if, line elf, brush curl middle brush of W, wire d to thepositive pole. The relay 220 then opens its contact 216 and thus breaksthe circuit of the motor magnet 214 causing the slow-acting finder LF tostop on the line of the calling subscribed 8 The moment thequiclractingfinder F, established the connection with the calling linethe line control relay LR in the group selector was energized by acurrent that commenced flowing from the battery B through the upperwinding of the relay LE, (6,, 221, 204, 223, 224, 148, a, brush set V waa calling subscribers station S 6 105,, brush of brush set W 5, 149,225, 226, 203, 222, 5,, 223, lower winding of relay LR, hack to battery13. The line control relay is energized by this current and closes itscontacts 225, 228 while opening its colitacts 226, 227. Meanwhile therelay 231 will also have been energized by a current through 231, 232,contact 233 of the oil'- normal switch 03 to earth. Thus as soon as therelay LR is energized a current flows from the negative'battery polethrough 234, release relay RR, contact 228, wire 2135 to earth. Therelease relay closes its contacts 236 and 237 and opens its contact 238.The contact 236 closes the circuit of the relay 239 of the slow-actingfinder which may be traced from earth through 236, 240, 239, brush cf,wire cf cut-off relay 00 to the negative pole. Thus the cut-off relay 00now receives current over two paths, the one leading rom earth through236 and relay 239, and the other from earth through the relay CR,contact 14 6, 147, wire 0, etc., over the path already traced.

As soon as the cut-of]. relay co is energized by the current that flowsthrough the relay CR the line relay Z of the calling line is deenergizedand opens its own locking circuit at its contact 104 and also thecircuits or" the relays m and M that control the circuits of the motormagnets of the quicltacting finder. The line relay also discounects thepermutation wires 5 and S) from earth. The finder starter FS is alsodeencrgized and reconnects the common battery lead 111 to the other linerelays oi the group at 110. The retraction of the armature 116 does not,however, cause a closure of the starting circuit by the contact 117.

The opening of the earth connections of the permutation wires 5 and 9causes the deenergization of the test relays s3) and 25p and theserelays by closing their contacts 135 and 136 prepare the circuits of themotor magnets of the quick-acting line finder the complete closure ofthese circuits being prevented by the contact 134 being kept open by therelay CE.

The connecting relay GB is still kept energized by the current whichflows from earth through CR, 146, 147, c, wa 0 and 00 to the negativebattery pole.

If another subscriber in the same group were now to call anotherquiclcacting finder F 2 would connect to the line of this subscriber andextend it to another idle slowacting finder LF or group selector G14 Ifthe subscriber that has been connected in tie manner described to anidle group selector GlV desires a connection with subscriber No. 354 hefirst sends a series of three impulses through the relay LR. At eachinterruption of the line loop of the calling subscriber the line controlrelay LR lets its armature drop back so as to close a circuit from thenegative pole through 234, 226, 241, 237, lifting magnet HM of the groupselector to earth. The lifting magnet is energized three times and liftsits set of brushes cg, by, 09 to the third contact row of the selectorwhich for convenience will be assumed to be of the well known Strowgertype. After the third interruption of the calling subscribers loop theloop is kept steadily closed and the line control relay keeps itsarmature attracted so that the change over relay CR, which is energizedduring the oscillations of the armature of the line control relay by acurrent flowing from the negative pole through 234, RR, CR to earth, issteadily short circuited by the contact 228 and lets its armature dropback. The contact spring 242 then presses against contact 230 and movesit away from the contact 229. A short circuit closure is effected duringwhich an impulse fiows from the negative pole through 234, 225, 229,230, 242, 243, side switch magnet 3M to earth. The off-normal contact243 is closed the moment the group selector executes its first verticalstep. By the impulse through the side switch magnet SM the contact armslll) tor; so that on the first attraction of the armature of the rotarymagnet not only the.

brushes or wipers ag, bg, cg are turned one step but also the armatureof the side switch magnet SM, is pressed against its pole iece. When thebrushes cg, 6g, cg reach the first set of bank contacts or trunk theside switch magnet SM, will, if this trunk is busy, cause it will beenergized by a current that will flow from an earth connection inanother group selector that has already seized the trunk cc, releaserelay 255 of this group selector, contact arms 2416 and cg of the same,wire c u; brush cg, wire 256 of the group selector that is hunting for afree trunk, contact 246 and side switch magnet SM, of this selector tothe negative pole. The brushes ag, bg, cg are stepped around step bystep in a known manner until an idle trunk is found when the brush cgwill-engage with a trunk wire or that is only connected to the negativebattery pole through a relay 258 having a very high resistance. The sideswitch magnet SM will then let its armature drop back thereby causingthe contact arms of the side switch to shift into their third positions.This opens the circuit of the rotary magnet DM and disconnects the linecontrol relay LR- froin the line of the calling subscriber- The brush cgis connected through release relay 255 of low resistance to earth andthe trunk aw, be, cc is thus rendered engaged. In consequence ofthe'disconnection of the line control relay LR from the line a, 0, thisrelay and also the relay RR are deiinergized. If the relay ER isdeenergized before the side switch moves from the second to the thirdposition the release magnet AM of the group selector is energized by acurrent from earth through 238, 260, AM to the negative pole of thebattery. Therefore, if the calling subscriber were to replace hisreceiver on its switchhook beforev the group selector has had time tofind an idle trunk (02), be, 0 0 the closure of the contact 238 due tothe. de-- .energization of the release relay RR would cause the groupselector GVV to be restored to its normal position. This would alsoresult in the restoration of the slow-acting finder LF in the manner tobe presently 224, an, 245, are, 24.7, 248, 24 9, 250,

keep its armature attracted be described. The energization of therelease magnet AM would cause the closure of the circuit of the startingrelay 262 of the selector finder VS, Fig. 7 which may be traced from thepositive pole or earth through contact 261, wire 21 1, contact arm 205of the selector finder, relay 262 to the negative pole. The startingrelay 262 closes its contact 263 and a current impulse then flows fromthe negative battery pole through 263, rotary magnet Dlvic, interrupter26 i 'to earth. The rotary magnet DM shifts the contact arms 201, 202,203, 204i, 205, 206 one step forward and if the next trunk or groupselector is busy the locking circuit of the starting relay will be keptclosed. This locking circuit may be traced from the negative pole of thebattery through 262, 265, contact arm 206, wire 212, leading to the neXtgroup selector and then either through the contact 250 of the next groupselector to earth. If the trunk leading to the next group selector hasalready been seized by another selector finder the locking circuit ofthe starting relay 262 may also be completed through the co tact arm 206of this other selector finder and through the contact 266 of the same toearth. But as soon as a free trunk is found by the selector finder thelocking circuit of the relay 262 of the selector finder will not beclosed through a contact 236 nor through a con tact arm nor through acontact 266. The starting relay 266 then lets its armature drop back andopens the circuit of its rotary magnet DMV at the Contact 263. Theselector finder stops and connects the quick-acting finder F,associated. with it to an idle group selectorGYV.

When the starting relay 262 is energized a contact 265 is closed bywhich the restoring relay a l of the quick-acting finder F, isenergized. The restoring relay M then causes the quick-acting finder Fto return to its normal position in the manner to be described later.

The operations involved in the establishment of a connection between thesubscriber S and the subscriber No. 354 have been described up to thestage in which the group selector GTV found a trunk at, 72 22, cvleading to an idle final selector LlV. By the shifting ofthe side switchof the group selector GTV from its second to the third position the line05 1 is extended to the trunk (w, 101 and at the same time a relay 259is connected to the limb b, of the talking circuit in the groupselector. A circuit will then be closed from the negative battery polethrough relay 259, 251, L 222,203, 226, 225, 149, 7), brush of the.brush set W 10b Z2 subscrihers station S (r wa brush of brush set W a,148, 224i, 223, 204, 221, a 2&7, cg, at, upper winding of the throughthe contact 236 or.

.tive battery pole.

line control relay LR to earth. The relays LR, and 259 are energized.

At the moment the relay 259 is applied to the wire Z), the contact arm252 of the side switch also prepares the circuit of a slowacting relay261. The circuit is opened before the relay 261 has time to close it bythe energization of the relay 259 and the consequent opening or thecontact 263.

The calling subscriber new sets the wipers of the final selector ontothe tens group containing the wanted line by working his selectorcontroller and thus causing a series of five interruptions of his lineloop. At each interruption an impulse flows from the negative polethrough266, 269, 270, 271, 2'72, lifting magnet HM, of the finalselector to earth and the brushes of the final selector which, forconvenience, will be as sumed to be built like a Strowger selector, arelifted to the fifth contact row.

The interruptions of the calling line loop cause deenergizations of therelay 259. At each deenergization the relay 261 is energized by animpulse that flows from the negative pole through 252, 263, 261 to thepositive battery pole. Tt attracts its armature 26a and thus closes thecircuit of the side switch magnet SM, (earth, 264, SM,, negative pole).The relay 261 is slow-acting and keeps its armature contact 26% closedin spite or the openings er contact 263. But when the tens selectingimpulses have all been sent in and the calling subscribers loop is againsteadily closed, the contact 263 is opened tor a considerable time, sothat the relay 261" is given time to release its armature and to openthe circuit of the side switch magnet SM This magnet then lets itsarmature drop back and causes all the contact arms of the side switch toshift from their third to their fourth positions. This results in therelay 259 being disconnected from the wire 5 The contact arm 249 or" theside switch earths the wire 211 and thereby energizes a relay 280 in theslow-acting finder and the starting relay 262 in the selector finder.The circuit of relay 280 may be traced from earth through 2 19, 281,282, 280 to the nega- The relay 280 closes the contacts 283, 284iand285. By its contacts 283, 285 it establishes a connection between thecalling subscriber and the final selector LW.

The circuit of the starting relay may be traced from earth through 249,211, 205, 262 to the negative pole. It closes its con.- tact 263 andthus energizes the rotary or motor magnet DM of th selector finder whosebrushes are now caused to travel until they find a trunk leading to anidle slowacting finder or group selector. The relay 262 keeps thecontacts 223, 226 open while the finder is hunting in order to preventdisturbances in busy lines whose contacts happen to be traversed by thebrushes of the selector finder. As long as the brushes of the selectorfinder touch busy lines the looking circuit of the starting relay 262extending through the contact 265 and the brush 206 is kept closed inthe manner already described and this circuit is only opened when anidle trunk is found.

On the energization of the starting relay 262 a contact 265 is closed bywhich the re storing relay M of the quick-acting finder F is energizedin a circuit extending from earth through 265, 286, M, to the negativepole. The relay 'lZ opens its contact 1617 and thereby denergizes theconnecting relay CR which receives current up to that moment by way ofthe contacts 146, 1 1'? and the cut-off relay 00 of the callingsubscriber. The connecting relay opens its contacts 1 18, 1 19 whileclosing its contact 13 1. lly the closure of the contact 13-1 theinterrupter 133 is applied through 122 and 134 to the wire 138 whichconducts the impulses produced by the interrupter 133 through tiecontacts 135 and 136 to the pairs of motor magnets E E and E E Of eachof these pairs of magnets only the one (E resp. E that previouslyoperated in setting the quick-acting finder onto the 9 calling line willreceive impulses, for when the primary and secondary switches are movedtoward the bank contacts representin j the calling line their switchesDS D53 which are constructed like the switch do, F 3, always close thecontact C that corresponds the active motor magnet. Therefore in thepresent case the contact that corresponds to the magnet E and thecontact C corresponding to the magnet E are closed and when therestoring circuits are closed current impulses will flow, firstly fromthe negative pole through 133, 122, 134:, 138,135, E 0 DS to earth andsecondly from the negative pole through 133, 122, 134, 138, 136, E C DSto earth. In order to prevent these motor magnet circuits from beingopened by the test relays t2), s29 during the trailing of the guidebrushes 1V TV over the contacts of earthed permutation wires, thecircuits of these relays are kept open by the contact 141 of therestoring relay rZ, until the quick-acting finder regains its normalposition, in which the off-normal switch OS, opens its contacts 122 and120 and thus stops the flowing of the impulses through the magnets E Eand. opens the locking circuit of the restoring relay rZ. Thequick-acting finder F, is now ready to connect another calling line tothe idle group selector which by this time will have been found by theselector finder VS associated with the quick-acting finder.

As the selector finder VS has made a connection with a different groupselector 'GlV than the one used for the desired talking connection thecircuit which extended from the negative battery pole through 219, 202,208, elf, elf, 'wd brush of brush set "W 03 to the the negative pole isbroken and the relay 220 closes its contact 216. Butthe circuit of therotary magnet 21 1 of the slowacting finder is kept open by the relay239' which is energized in the same circuit as the cutoff relay 00 andkeeps its armature contact 215 open.

During the steady closure of the loop of the calling subscriber, whichoccurs after the final selector LW has been made to select the desiredcontact row, the side switch of the final selector is moved from itsfirst into its second position by an impulse which flows from thenegative battery pole through 266, 267, 290', 291, 292', 293, sideswitch magnet SM to earth when the change over relay CR lets itsarmature drop back.

The operation of the relay set LE R11 CR that governsthe actions of theV final selector corresponds to that of theset of controlling relays inthe group selector so that a detailed description of this operation isunnecessary. I 1

By the shifting ofthe contact arm 2720f the side switch into its secondposition the rotary magnet DM is connected to the selecting or steppingcircuit 270 of the final selector. Furthermore the negative pole of thebattery is connected by the contact arm 294: to the lower winding of theline control relay LE and this connection substitutes the connection tothe limb Z), of the talking circuit that was disconnected in the groupselector from this limb by the disconnection of the relay 259. Thesubstitutional connection with the negative pole through the I. contactarm 294 is made before the relay 259 in the group selector isdisconnected from the limb b, by the shifting of the contact arm 251from its third to its fourth position. This retarded disconnection ofthe relay 259' is caused by slow-acting relay 261 letting its armaturedrop back slower than the relay CR Since the circuit including the sideswitch magnet SM, and the contact 264' is opened later than the circuitof the side switch SM, is closed, the side switch magnet SM causes theside switch of' the group selector to move into its fourth positionlater than thesi'de switch magnet SM, connects the. negative batterypole through 294 and the lower winding of the line control relayLR tothe b-limb of the talking circuit. Thus, during, this change of circuitsno deener'gizatio'n of the'li ne control relayLR takes placef It nowreceives current over the following path: negative pole of battery,lower winding of the line control relay LE be, by, 2&8], 285, bf,

l ss) 59) 59 @5319 fss '1: 7 9 a0), upper WlIlCllngOf relay LR earth.

The calling subscriber, who desires a connection with station No. 354,now sends in a series of four units selecting impulses which causes fouroscillations of the armature of the line control relay LE The relays BBCR, are kept energized during these oscillations and each time thearmature of L3 falls back a current impulse flows from the negativebattery pole through 266, 269, 270, 271, 272, rotary magnet Dhf -toearth. The rotary magnet turns the brushes a b 0 four steps placing themin contact with the fourth line in the fifth contact row of the selector2'. e. in contact with the desired line No. 354. When the selectingimpulses cease the calling subscribers loop is again steadily closed andthe change over relay GR, is caused to release its armature by its beingshort-circuited at 268. When the armature of the change over relay dropsback it closes the change over circuit which extends from the negativepole through 266, 267, 290, 291, 292, 293, side switch magnets SM toearth. The side switch of the final selector is now shifted into itsthird position and its contact arm 297 closes the cir-.

cuit of the test relay 300 which extends from earth through 297, 300,cs, 0Z,,, 0 cutas relay 00, of the wanted line to the negative pole. Ifthe desired station is free the test potential on the test wire cZ willbe highenough to cause the energization of the test relay 300. Thisrelay then attracts its armature and closes the contacts 301, 302

The closure of the latter contact causes the ringing relay BL to beenergized (negative pole, 302, 303, RL, earth). The relay BL closes itsarmature contacts 304, 305 thereby connecting the ringing currentmachine LM to the brushes a whereupon a ringing current flows from theringing machine through the ringing cut-off relay 307, 30%. a M (0wanted station S Z9 El 6 305, interrupter 306, back to ringing machineLM. The moment the called subscriber responds to the call by removinghis receiver from its switchhook, the ringing current flowing throughthe relay 307 is strengthened sufliciently to cause this relay to closeits armature contact 308 so as to energize the relay 309 (negative pole,308, 309,

'earth). The relay 309' then closes its looking circuit, which extendsfrom earth through 309, 310, 311' of the ofi-normal switch to thenegative pole, and at the same time it opens at contact 303the circuitof the ringing relay RL causing this relay to open its contacts 304, 305while closing. the contacts 312; 313. Since the contact arms 295', 296are in their third positions the called subscriber now receives a enemafrom the battery which flows through the lower winding ofthe relay A3296, 313, 6 M

214 which circuit extends 6 S a aZ a 312, 295, upper winding of AR backto the battery B The relay AR, attracts its armature v314 which thenbrushes past the contact spring 315.

It the called subscriber is the first to replace his receiver on theswitchhook the current flowing through AR, will cease whereupon thearmature 314 falls back and brushes past the spring 315 pressing itagainst the spring 316. This causes a current impulse to flow from thenegative pole through 316, 317, 318 of the oft-normal switch, releasemagnet AM of the final selector to. earth, whereby the final selector isreleased. At the same time a circuit is closed from the negative polethrough 315, 316, 317, or), cg, 246, release relay 255 of the groupselector to earth. The release relay 255 closes its contact 320 thuscausing the release magnet AM of the group selector to be energized by acurrent flowing from earth through 320, 253, AM to the negative batterypole. This restores the group selector to its normal position and themoment the contact 250- of the side switch of the group selector severethe connection between the wire 321 and earth the locking circuit of therelay 280 and also the circuit of the relay 239 are interrupted. Therelay 280 severs the connection between the brushes a 5; and the wires ab, and thus prevents disturbances being caused in busy talking circuitswhich may be momentarily touched by the brushes af, bf, while travelingback into their normal positions. The falling back of the armature ofrelay 239 causes the closure of contact 215 and therefore the closure ofthe circuit of the rotary magnet through 216, 215, 214, 217, interrupter218, to the negative battery pole. The rotary magnet 214 then rotatesthe brushes a), bf, of, (Zf until they reach their normal position inwhich the off-normal switch OS opens the contacts 233, 217. The thecontact 217 causes the circuit tary magnet 214 to be broken motion ofthe set of brushes a7, bf, of, (Zf.

lVhen the final selector reaches its normal position and opens thecontact 311 the relay 309 is deenergized by the opening of its lockingcircuit and all the apparatus is then restored to its normal position.

If the calling subscriber is the first to abandon the connection hisreplacing of the receiver will cause the steady closure of the contact323 and the short-circuiting of the release relay RR This relay thenlets its armature drop back so as to close the contact 322. Thisconnects the negative pole through 322 and 317 to the wire 0., whichenergizes the release magnet AM or" the final selector and the releaserelay 255 of the group selector. The restoring operation is thuscommenced and it progresses in the same way of the roand stops the fromthe earth opening of as it did when started by the called subscriber.

If the desired line is busy when the last change over impulse is sentand the side switch shifts into its third position the test relay 300will not be energized and a tone giving device 325 will be connected tothe line a through 326, 325 and 324. The calling subscriber thenreceives a busy signal and replaces his receiver on the switch-hookthereby causing the restoration of all devices to their normal positionin the manner already described.

Special attention will now be called to circuits for stopping theslow-acting finders on calling lines.

The circuits for this purpose contained in Figs. 5, 6, 7 and 8 are shownby themselves in Fig. 11 in order that their functions may be moreeasily explained. arranged as shown in this figure it would be possiblefor two slow-acting finders to make connection with one and the samecalling line. Assuming for example that the quick-acting finder F isconnected by its associated selector finder to the slow-acting finderLR, that the line Z calls and that the quick-acting finder F makesconnection with this line. The slow-acting finder LF will now also makeconnection with the line Z Suppose now that while that connectiondesired by the calling line Z is being extended by the other selectors(group selectors, etc.) to the wanted line another subscribed Z callsand that this second call is taken by another quick-acting finder Fwhich is connected by its selector finder to the slow-acting finder LFIt could now happen that the slow-acting finder LF, reaches the contactsof line Z before the first quick-acting finder F has been disconnectedfrom this line. The relay 320 that opens the circuit of the rotarymagnet DM of the slow-acting finder would then be ener gized by acurrent through the wire of the line Z that is connected by wrl, to thepositive polo of the battery and consequently a second slow-actingfinder LF, would be connected to the calling line in addition to thefinder LF,. The second calling line 2 will not be properly connected.

In Fig. 12 circuits are shown by which the above described undesirableoperations of the slow-acting finders are prevented. T Vith thesecircuits the motor magnet (DMa, DMb) of the slow-acting finder (LFa,LFL) used for a connection is first caused by a starting impulse, in themanner described in con nection with Figs. 5, 6, 7 and 8, to move theslow-acting finder out of its normal position and to be connected to aninterrupter 21864. This results in the closure of an oil-normalcontactJcz, Fig. 12, which closes the circuit of a relay 32064. Thiscircuit extends from the brush of the selector finder (c. g 3025) thatjust happens to be connected to the slowl/Vith the circuits

